(1) Field of the Invention
The present invention relates to a device for electrically powering at least one piece of equipment of a rotor, and also to an aircraft including such a device.
The invention lies in the technical field of means for electrically powering a rotary member, and more particularly de-icing/anti-icing members of a rotorcraft rotor.
(2) Description of Related Art
Certain aircraft are provided with devices for de-icing/anti-icing airfoil surfaces, in particular blades of a rotor. The problem of such airfoil surfaces icing is well known in the aviation industry, it being possible for the aerodynamic profile of such surfaces to be modified unfavorably as a result of ice forming in flight because of impacts against droplets of supercoiled water contained in the atmosphere. This problem is often countered by fitting the airfoil surface with a heater structure.
However, it will be understood that it can be difficult to deliver electrical power to equipment present on a rotary assembly from an electricity generator that is present in a stationary frame of reference within the airframe of the aircraft.
Various devices are known for conveying electricity to a rotary assembly that is permanently and irreversibly mounted on propellers, in particular propulsive propellers or wind turbines.
Document FR 2 553 596 describes a propeller including electricity generator means within its hub for powering an electrical system for changing the pitch of propeller blades and de-icing means.
Document EP 0 629 318 describes using a magnet free to rotate between two sets of windings arranged within a propeller.
Document EP 0 777 602 includes a generator having winding carried by a rotor, the windings co-operating with a stationary permanent magnet.
Document EP 2 218 643 describes an electrical machine arranged in a propeller for electrically powering electrical resistors. The alternator has a stator secured to a stationary casing of the propeller and windings secured to a rotary mast of the propeller.
Document US 2011/0024567 describes apparatus arranged in a turboprop having two contrarotating propellers in order to generate electricity.
The same applies to document GB 584 563.
Document WO 2010/015359 describes electricity generators arranged on a wind turbine propeller for feeding electricity to means for modifying the pitch of blades of the propeller, each generator having a rotary portion co-operating with a toothed ring in the nacelle of the propeller.
It can be seen that some of the above documents do indeed relate to airplanes that might fly in clouds loaded with super cooled droplets of water such that they are always faced with the problem of icing. Under such circumstances, it can indeed be useful to arrange an electrical power supply device permanently in the propeller of such an airplane for de-icing or anti-icing purposes.
Likewise, a device for powering electrical means for varying the pitch of a propeller may be present on a permanent basis in that propeller.
However, certain aircraft, and in particular rotorcraft, do not require such an electrical power supply device to be installed permanently.
Consequently, a device is known that is provided with an alternating current (AC) generator connected to an electrical unit sometimes referred to as a “power de-icing unit”. The electrical unit is provided in particular with an electrical rectifier and a sequencer for powering a plurality of electric cables in a predetermined sequence. Furthermore, as a safety measure, the electrical unit is duplicated.
The generator and the electrical unit are installed in a stationary frame of reference, i.e. the airframe of a rotorcraft.
Consequently, the device has a slip ring unit comprising a non-rotary portion and a rotary portion, which portions are connected together by a system of brushes rubbing against rings. The non-rotary portion may for example possess circular rings that are electrically powered by electric cables coming from the electrical unit, while the rotary portion has respective brushes traveling over the rings.
The slip ring unit can be mounted reversibly so as to be used only during winter periods or only for particular missions. Nevertheless, such a slip ring unit is very heavy and difficult to put into place, in particular because of the presence of a large number of electrical cables of large dimensions and because of the presence of the slip rings themselves.
Furthermore, friction between each brush and the corresponding slip ring tends to degrade the performance of the slip ring unit. Maintenance actions requiring the device to be dismantled then need to be undertaken relatively often. Unfortunately, the slip ring unit is sometimes difficult to access, so the cost of maintenance can be high and the rotorcraft can be out of service for a long time.
Document FR 2 960 516 describes a device for electrically powering and controlling equipment on a rotor. That device has a three-phase AC generator arranged in a stationary reference frame, and a rotating field transformer having a stationary portion connected to the generator and a rotary portion that is connected to a sequencer, which is arranged in the rotary reference frame.
That device is advantageous in that it avoids using a slip ring unit with brushes.
Document U.S. Pat. No. 5,572,178 describes a rotary transformer having primary and secondary windings and magnetic circuits for optimizing the passage of magnetic field lines.
An electrical power supply device is also known for powering at least one piece of equipment on an aircraft rotor that is driven by a mast. That device comprises a removable pole suitable for being reversibly secured to the mast. The pole also includes an upper alternator and an upper tube suitable for being constrained to rotate with the mast, the upper alternator having a plurality of upper windings that are fastened to the upper tube, the pole having a shaft carrying at least one upper permanent magnet of the upper alternator. A mechanism then allows the shaft and the upper tube to perform distinct rotary movements.
That device is thus a removable device.
Documents GB 2 264 812 and GB 2 293 522 are also known.